On 2/27/19 4:48 PM, Achilleas Mantzios wrote:
On 27/2/19 4:16 μ.μ., David Steele wrote:
On 2/27/19 2:31 PM, Achilleas Mantzios wrote:
On 27/2/19 1:58 μ.μ., richter@xxxxxxxxxxxxxx wrote:
Just to notice, I d o use backup from standby and WAL archive from
standby. It is possible. But you have to configure standby with
option of wal archive "always".
I guess there are issues with it. If this was so easy then pgbarman
and pgbackrest would support it out of the box.
There are a few issues with it:
1) If you allow the primary and standby to archive to the same
repository then there needs to be some conflict resolution if they
write at the same time. If they write to different repositories then
you need to decided which one to use for a restore, or have some kind
of conflict resolution between them. It gets complicated.
2) Writing only from the standby reduces load on the primary but if
the connection to the primary is down then you can get behind on
archiving. If something then happens to the primary then your recovery
point will be limited.
David to quote an older email from you:
"pgBackRest currently requires some files and all WAL to be sent from
the primary even when doing backup from standby. We may improve this in
the future but it's not on the road map right now. "
So, I had the impression that receiving WALs from the standby was a
greater technical problem.
No, it just increases the risk of being behind on archiving.
One of the things pgBackRest does well is move a *lot* of WAL and it is
orders of magnitude faster than streaming replication, which is
single-threaded and uncompressed. So, in spite of the additional load
it's generally safest to archive from the primary, especially on high
write volume clusters.
--
-David
david@xxxxxxxxxxxxx
